The use of intra-aortic balloon counterpulsation (IACP) for low cardiac output complicating acute aortic insufficiency is controversial. Beneficial effects of diastolic augmentation are offset by conflicting and poorly documented reports of altered coronary blood flow and theoretical increases in regurgitant volume and left ventricular wall tension during IACP use. We have found that regurgitation is not significantly increased by IABP during acute severe AI in dogs. Preliminary data have not demonstrated deleterious effects of IACP on myocardial metabolism, coronary blood flow or ventricular function during aortic insufficiency.